LaxSr1-x(Mn, Fe, Co)O3-delta, and BaySr(1-y)CoO(3-delta) perovskite oxide powders were investigated as potential thermochemical energy storage (TES) materials operated at high temperatures above 600 degrees C. The purpose of the research is to provide complete characterization of the impact of partial A- and B-site substitution on the reactivity, kinetics, redox reaction repeatability and charging/discharging storage capacity. The perovskite oxides were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) at temperatures of 500-1100 degrees C. Thermal energy storage was evaluated in terms of the enthalpy of the reversible reactions of oxygen release (reduction) and uptake (oxidation) upon heating the oxide materials in air stream. Among the perovskites tested, Ba0.3Sr0.7CoO3-delta and Ba0.7Sr0.3CoO3-delta powders were suitable thermochemical storage materials operating at above 600 degrees C in terms of chemical reactivity, charging/discharging temperatures and storage capacities, kinetics of oxygen uptake/release, and repeatability of thermochemical cycling. Further, charging/discharging capacity for both perovskites was comparable to that for Fe-doped manganese oxide. (C) 2019 Elsevier Ltd. All rights reserved.